AstraZeneca might have included outdated information from a clinical trial of the Covid-19 vaccine it has developed with Oxford university, a US federal health agency said on Tuesday, throwing previously published positive results into doubt.

In a rare move, the National Institute of Allergy and Infectious Diseases said it had been notified by the trial’s data and safety monitoring board that “it was concerned by information released by AstraZeneca on initial data from its Covid-19 vaccine clinical trial”.

“The DSMB expressed concern that AstraZeneca may have included outdated information from that trial, which may have provided an incomplete view of the efficacy data,” the NIAID said. The group is led by Anthony Fauci, an adviser on coronavirus to the US president.